1. Field of the Invention
The present invention relates to a light pen, and more specifically, to a light pen capable of adjusting a beam area of a light source projected on an optical touch panel.
2. Description of the Prior Art
In general, a beam projected by a light pen is usually utilized as input of photo signals to a conventional optical touch panel, and light sensing elements disposed inside the optical touch panel are utilized for sensing the said photo signals. As far as input of X-axis and Y-axis information to the optical touch panel is concerned, the optical touch panel utilizes photo TFTs (Thin Film Transistors) disposed therein to determine locations of the photo signals by transforming the photo signals into corresponding photo currents, so that a user can perform X-axis and Y-axis operations on the optical touch panel (e.g. moving a cursor, or rolling a scroll). On the other hand, for input of Z-axis information to the optical touch panel, the optical touch panel calculates Z-axis information according to a beam area of the light pen projected thereon so that a pen pressure generated by the user can be determined accordingly. In such a manner, the user can perform Z-axis operations on the optical touch panel (e.g. selecting a function icon). In summary, via the said sensing method, the user can directly perform the said operations on the optical touch panel by a light pen without pressing the optical touch panel.
The said light pen usually projects a beam of a fixed area. Therefore, if the user wants to adjust the beam area of the light pen projected on the optical touch panel for performing Z-axis operations (e.g. selecting a function icon), the user needs to hold the light pen in mid-air and then adjust a position of the light pen relative to the optical touch panel so as to change the beam area. However, since the user needs to hold the light pen in mid-air, the said method usually makes the user incapable of inputting Z-axis information steadily and operational problems may therefore occur (e.g. incorrect sensing of the optical touch panel).